1. Field of the Invention
The present invention relates in general to a magnetic head formed by bonding together a pair of core halves with a predetermined gap length provided therebetween. In particular, the present invention may be applied to a magnetic head in which magnetic film of an Fe-Si-Al alloy is employed and which is suitable for use as a high-density recording head applicable to the use of high frequencies and capable of meeting the requirement for a high S/N ratio, mainly as, e.g., a video head or a computer head.
2. Description of the Related Art
In the field of magnetic recording techniques, there have recently been remarkable improvements in the recording density achievable. In step with this, in the case of, for instance, magnetic heads which act as electromagnetic transducers, it is increasingly required that the width of the tracks be reduced, that the level of saturation magnetization of the core material be elevated, and that the magnetic permeability in high-frequency zones be enhanced.
In recent years, magnetic heads of certain types are receiving expeditious attention as being capable of meeting the above-mentioned requirements in the field of magnetic recording. These types include thin-film laminated magnetic heads in which magnetic film of an Fe-Si-Al alloy is employed. An example of a magnetic head of this type is shown in FIGS. 2 to 4. Referring to these figures, the structure of the magnetic head will be briefly described.
Referring to FIG. 3, a substrate 11 of the magnetic head is formed of crystallized glass or a ceramic material. A thin film 12 of an Fe-Si-Al alloy is formed on the surface of the substrate 11 with a film thickness of 1 to 20 .mu.m. Subsequently, a non-magnetic dielectric film, or an interlayer film 13 which is formed of SiO.sub.2 is formed on the magnetic alloy film 12 with a film thickness of 0.03 to 0.5 .mu.m.
Further, the operation of laminating a magnetic film 12 and a non-magnetic dielectric film 13 is repeated a required number of times so as to form a magnetic-film structure body 14. The thickness of the magnetic films 12 and the non-magnetic dielectric films 13 as well as the number of the laminating operations are suitably set in such a manner that the thickness of the portion where they are laminated is equal to track width w (see FIG. 3).
Subsequently, a glass film 15 is formed on the magnetic-film structure body 14, then another substrate 16 is laminated on the glass film 15. Bonding glass is used as the glass film 15. The substrate 16 is formed using the same material as the substrate 11.
A laminated film structure body 17 prepared in this way, is then cut in the thicknesswise direction in which the body 17 is laminated, thereby forming a pair of core half blocks 18 and 19, as shown in FIG. 2. At least one of the core halves, the core half 18 in the illustrated example, is formed with a coil groove 20.
Subsequently, in order to achieve a firm bond between the mating surfaces of the core halves 18 and 19, chamfered portions 22 have hitherto been formed in the surface opposite to the coil groove 20, i.e., in the two lateral side surfaces of the core half 19 in this example, as shown in FIG. 2. Further, those portions of the core halves 18 and 19 which are on the side remote from the coil groove 20, are formed with recesses 23. Thereafter, the mating surfaces of the core halves 18 and 19 are subjected to polishing works. Then, a gap portion 21 is formed.
Thereafter, the core halves 18 and 19 are mated, with their mating surfaces facing each other. Molded glass is charged into the chamfered portions and the recesses, thereby joining the core half blocks.
Finally, R (radius) polishing works and other forming works are performed to form the tape sliding surface, and coil winding is also performed, thereby obtaining a magnetic head 10.
With the magnetic head 10 having the above-described construction, it is very important to finish the gap portion 21 formed on the mating surfaces of the pair of core halves 18 and 19 in such a manner that the portion 21 has predetermined dimensions and a predetermined configuration. If the finished gap portion suffers from any edge sagging, collapse, or spreading, this may cause great deterioration in the characteristics of the magnetic head.
As shown in FIG. 5, the gap portion has conventionally been formed by forming non-magnetic dielectric layers 25 and 26 of SiO.sub.2 on the gap portion forming surfaces of the core halves 18 and 19, forming bonding glass layers 27 and 28 on the corresponding layers 25 and 26, bringing the bonding glass layers 27 and 28 associated with the corresponding core halves 18 and 19 into mutually facing relation, and fusion bonding the facing glass layers 27 and 28.
The magnetic head having the above-described arrangement possesses very good magnetic characteristics. However, in the manufacture of magnetic heads of this type, the gap portions 21 have to be formed in greatly varying yields. Sometimes, a high yield on the order of 70% may be continuously achieved. At other times, the yield may be as low as 0% or thereabouts if, for instance, the gap portion suffers from improper fusion bonding, and such low yields may continue. Repetition of these conditions may result in a yield of only about 5% per month in the worst case. Thus, the efficiency of manufacture has been very low.